There are various ways of saying that something consists of something else:
- composed of
- comprised of
- consist of
Maybe there are more. Are there hard and fast rules when to use which or are they synonyms?
Here are some thoughts:
There are some works relating the relatively mature field of mereology to natural languages; Wikipedia barely mentions them. I am not an expert on this particular crossroads, but I'm afraid that the ambiguity of natural language won't let you find hard and fast rules as you request. "Parts: A Study in Ontology" by Simons 1987 is the work that I know best about this, and you may find it useful if you are interested in a detailed study of the matter.